JPH0361761B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved process for dry spinning polymer solutions into filaments. In more detail,
The method of the present invention involves flowing a heated inert gas across the filaments exiting the spinneret and directing the gas stream downward into the hollow center of the bundle of filaments.

Dry spinning is a well known method for producing filaments from soluble polymers, and equipment for dry spinning is also known. In a typical dry spinning process, a hot polymer solution is extruded through a series of concentrically arranged spinneret orifices.
A sheath of hot inert gas, called a suction gas, is then introduced at the top of the spinning apparatus to rapidly evaporate the solvent, forcing the gas to flow downward around the exiting filament.

Wier, US Pat. No. 3,737,508, describes a method for removing a portion of the suction gas upward through the center of the spinneret. In the wire center suction method, by applying a vacuum to a conduit attached to the center of the spinneret head, a portion of the suction gas normally introduced is forced to exit near the exit face of the spinneret. Pull vertically across the filament. This allows fresh gas to contact the filament just below the spinneret, before forming a skin on the surface of the filament.
The effectiveness of removing solvent in the critical zone increases.

The present invention is generally a method of enhancing central flow as a supplement to wire central suction methods.

In the enhanced central flow process of the present invention, the filament is centered inside the filament bundle near the spinneret face;
A Coanda type gas flow capture device is used which is supplied with a small stream of pressurized inlet gas. Coanda's device captures gas from within the center of the filament bundle, thereby enhancing the gas flow internally through the filament bundle. Instead of being withdrawn from the spinning device as in the center suction method, the gas flow is redirected into the interior of the aggregated moving filament bundle. This supplies gas to the hollow interior of the moving filament bundle,
The boundary layer effect of this filament bundle (boundary−
gas is quickly sucked downward due to layer effect). By satisfying this suction requirement, the stability of the filament is improved.

The spinning process of the present invention involves (1) extruding a solution of polymer through a spinneret having orifices arranged in a pattern to form a hollow bundle of filaments; treating the filaments by directing a stream of heated inert gas downwardly and/or inwardly; (4)
This includes directing a portion of the first gas stream downward and captured by the second gas stream. The net result of this is an enhanced gas flow inwardly through the filament bundle and downwardly within the center of the bundle.

The method of the invention may also include the step of creating a vacuum in the center of the hollow bundle of filaments proximate the spinneret face to assist the first gas flow to flow inwardly through the bundle.

1 and 1A, a polymer solution supplied from a source (not shown) is injected into heater 10 as indicated by arrow 11. Referring to FIGS. The heated polymer solution is then distributed to the spinneret 12a. This spinneret has 14 filaments.
It has a number of concentric holes or orifices arranged to create a hollow bundle of. A generally cylindrical case or chimney 16 is spaced radially outwardly from the spinneret assembly 12 and extends from a level above the spinneret assembly 12 to well below it. A connection 18 is provided for injecting a heated gaseous evaporative medium (suction gas) into the chimney 16. A generally annular air chamber 20 directs the medium downwardly around assembly 12 and through the annulus of filament 14 through a diffuser 22 or the like (ie, a first flow of heated gas). The schematically illustrated conduit 24 connects the heater 10 and the spinneret assembly 1.
2 and the lower end communicates with the hollow center of the bundle of filaments 14. conduit 2
The upper end of 4 is connected to a vacuum system to perform the central suction method described in the wire patent.

In the improved method of the invention, one end is connected to a source of pressurized gas (i.e. a second gas stream heated during passage through heater 10), preferably nitrogen, and the outlet end is spun by support 31. Base assembly 1
Coanda-type flow capture device 3 attached to 2
Use conduit 26 connected to 0. The Coanda principle is known and involves a device for applying fluid flow to a solid surface. One such device using this principle is shown in more detail in FIG. In FIG. 2, the supply gas, i.e. conduit 26
A second gas stream from enters device 30 at inlet 32 and is routed through annular manifold 34 and flows over curved surface 36 as it exits from annular manifold 34 through groove 38. This second flow, indicated by arrow 33, is directed in one direction through the semicircle (torus) created by the Coanda attachment to the internal curved surface 36 of the Coanda device 30. The second stream 33 captures the first stream of heated ambient gas as indicated by arrow 35.

In operation, the device 30 traps gas in the center of the bundle of filaments, creating a flow across the face of the spinneret 12a, as in a center suction process. Rather than being drawn out of the chimney 16 as in the patented central suction method of wire, this flow is redirected into a bundle of aggregated filaments moving downwards. This supplies gas into the hollow interior of the moving filament bundle, which gas is rapidly sucked downward due to the boundary layer effect. By satisfying this suction effect, the stability of the filament is improved.

The spinning direction of the present invention can be carried out using a Coanda apparatus 50 as shown in FIG. This particular device is attached to the spinpack containing spinneret 12a by bolts 51 extending below the underside of the spinneret. This device is Washashier 5
5, including a tapered tip 53 and a contoured wall 57 spaced from and surrounding the tip. This tip is threaded onto a bolt 51 to hold a washer 55 in position between the spinneret 12a and the tip, creating spaces 52a and 54a between the tip and the washer and between the washer and the spinneret. . The body of the bolt 51 includes concentric passages 52, 54 that connect at the other end with pressurized gas and vacuum, respectively.

In operation, the central suction gas is drawn through space 54a and passageway 54, while the gas flow flows downwardly through passageway 52 into space 52a, then along surface 53a of tip 53, until facing downwardly in the direction of wall 5 as indicated by arrow 56.
7 and the surface 53a of the tip.

In yet another embodiment of the Coanda device shown in FIG.
1 and a lower body portion 62. The upper body portion 61 including the cavity 61a is screwed to a bolt 64 extending from the spinning device.
The bolt includes a central passageway 64a that communicates at one end with a source of pressurized gas, indicated by arrow 65, and at the other end with a cavity 61a that leads to a periphery of body 60. 61b.

In operation, low pressure gas passes through passage 64a to cavity 61a and from there to the surroundings of Coanda body 60 through passage 61b.
The flow flows over the surface of the body 60 and flows downwardly in one direction, trapping ambient gas in a manner similar to that shown in FIG.

For optimal operation, the gas jet of the Coanda device must be in the turbulent range. By making the jet slot 61d as narrow as possible, the trapping effect is also enhanced. The gas flow path (through passage 61c) before the outlet can be modified to meet specific mechanical constraints.

It has been found that when the improved method of the present invention is used in conjunction with dry spinning equipment, productivity is increased without any adverse effects.

[Brief explanation of drawings]

FIG. 1 is a partial schematic vertical cross-sectional view of a dry spinning apparatus generally illustrating the method of the invention, and FIG. 1A is an enlarged partial view of FIG. 1 showing a flow capture device. FIG. 2 is an embodiment of a Coanda-type flow trap, FIG. 3 is a cross-sectional view of a second arrangement of a Coanda-type flow trap, and FIG. 4 is a diagram illustrating a method of carrying out the method of the invention. FIG. 3 is a cross-sectional view of yet another embodiment of a Coanda-type flow capture device useful in .

Claims (1)

Claims: 1. Extruding a polymer solution through a spinneret having orifices arranged in a pattern to create a hollow bundle of filaments, and directing a first stream of heated inert gas around the bundle of filaments. A method of spinning comprising the step of treating the filaments by flowing the filaments downwardly and inwardly through the filament bundle into its hollow center, in which a second flow of inert gas is directed near the spinneret and into the interior of the filament bundle. , along a centrally located Coanda surface, thereby capturing a portion of the first gas stream downwardly in the second gas stream. 2. The method of claim 1, wherein a vacuum is created in the center of the hollow bundle of filaments near the face of the spinneret to assist the first gas flow to flow inwardly through the bundle of filaments.